The present invention relates to a backlight for illuminating a display section including a liquid crystal display element and an operation section including button switches. More particularly, the invention relates to a backlight device and a backlighting element, which are constructed with an EL panel, LEDs, lamps and others.
There is known a device equipped with a liquid crystal display panel (referred to as an LCD panel) having a liquid crystal display element (LCD) and an operation panel including panel switches associated with operation buttons. Recently, this type of device has been equipped with a backlighting function to illuminate the reverse side of the display section and the operation section in order to render display characters and characters on switches to be legible even in a dark place. In this type of communication device, those characters must be legible in every use condition. Therefore, the backlighting function is indispensable in particular for mobile communication devices, such as portable phones and pagers.
An electrical arrangement of a device with a conventional backlight device is shown in FIG. 12. As shown, the device is made up of a display unit 101, a backlighting element 102, a backlight driver 103, a control unit 104, a switch 105, and a power supply 106. The display unit 101 includes a LCD for displaying characters, for example. The backlighting element 102 includes an EL (electroluminescence) panel for illuminating the back of the display unit 101. The backlight driver 103 drives and controls the backlighting element 102. The control unit 104 controls the display unit 101 and the backlight driver 103. The switch 105 is provided for backlighting. The power supply 106 is used for supplying electric power to the whole device.
FIGS. 13 and 14 cooperate to show a structural arrangement including a display unit and a backlighting element. FIG. 13 shows a side view of a structure including the display unit and the backlighting element. FIG. 14 shows a plan view of the backlighting element. An LCD panel 101a forms a display unit 101. An EL panel 102a forms a backlighting element 102. The EL panel 102a is disposed on the rear side of the LCD panel 101a. Light emitted from the EL panel 102a passes through the LCD panel 101a, and is irradiated from the front broad side thereof. Thus, a structure in which a light is irradiated from the back of the LCD panel 101a is employed. A light emitting section 107 is formed in the EL panel 102a, while covering the entire viewing area of the LCD panel 101a. 
Characters and/or images are displayed in the display unit 101 under control by the control unit 104. In this case, the backlighting element 102 is lit in order to secure a satisfactory viewing in a dark place. To light the backlighting element 102, the switch 105 is operated. In response to this, the control unit 104 sends an operation instruction to the backlight driver 103. In turn the backlight driver 103 applies a drive signal having an AC waveform (e.g., a sinusoidal waveform, a triangle waveform, or a rectangular waveform) at the amplitude of, for example, 50 to 100 Vpp, to the backlighting element 102. Then, light emitting elements within the backlighting element 102 is excited to emit light and illuminate the display unit 101. Electric power consumed by the backlight driver 103 and the backlighting element 102, when those operate, depends on the area of and luminance brightness on the light emitting section of the backlighting element 102. The power consumed is generally 10 to 50 mA for the size of approximately 60 mmxc3x9730 mm. After the backlighting element is lit, the backlighting element 102 automatically lights off under control by the control unit 104 when the following condition is satisfied; viz., the user intentionally lights off the backlighting element or the device is not operated for a predetermined time (several tens seconds to several minutes).
In the conventional backlight device thus constructed, power consumption is large when the backlighting element is lit. When it is applied to the mobile communication devices designed placing emphasis on the portability, such as pagers, portable telephones, PHS terminals, and PDA terminals, reduction of the communication device entails a restriction on the power capacity of the power supply (e.g., a battery) Therefore, the lighting of the backlighting element will greatly influence the battery lifetime. In case where a battery used for such a communication device as an air zinc battery is small in capacity, when the backlighting element is lit to consume large power, the battery voltage will drop. A conventional measure, generally taken for this, is to reduce the power consumption by reducing the luminance brightness of the backlighting element.
Where the EL panel is used, a signal of an AC waveform, e.g., a triangle waveform, needs to be generated for a drive signal during the lighting of the backlighting element, and its power is large. Because of this, the drive signal will cause power source voltage to vary and produce unwanted spurious radiations. Those voltage variation spurious radiations will cause noise and deteriorate radio and acoustic performances of the backlight device. For this reason, additional components are required for noise shielding. Device complication and production cost increase result.
The enhancement of the device function increases the areas that are required for the display section and the operation section of the backlight device, and increases the backlight emitting area. With this, more electric power is consumed for securing a required backlight brightness. Therefore, the power consumption problem is more serious.
Accordingly, a first object of the present invention is to provide a backlight device and a backlighting element, which effectively suppress power consumption when the backlighting element is lit while keeping luminance brightness at a required level. A second object of the present invention is to provide a backlight device and a backlighting element, which makes the device free from the noise generated when the backlighting element is lit.
Aspect 1 defines a backlight device comprising: a backlighting element for illuminating the back of visually presenting means of a device; and drive control means for intermittently driving the backlighting element at appropriate timings when the backlighting element is lit.
In the backlight device of aspect 1, the drive control means lights on the backlighting element at appropriate timings, for example, at such time intervals as to make the user visually insensitive to flickering of the backlighting element or to make the user visually sensitive to its flicker but to allow the user to decipher characters, for example, on the visually presenting means. The result is reduction of the drive time of the whole device during the backlighting, and reduction of device power consumption.
Aspect 2 defines a backlight device defined comprising: a backlighting element for illuminating the back of visually presenting means of a device; and drive control means for temporarily stopping the driving of the backlighting element when a device portion being adversely affected by noise generated by operation of the backlighting element is operated, in synchronism with operation timings of the device portion.
In the backlight device of aspect 2, the drive control means temporarily stops the driving of the backlighting element when the device portion being adversely affected by noise generated by operation of the backlighting element, for example, the radio processing unit of a communication device, is operated, in synchronism with the device portion. With this, there is no chance that the noise by the backlighting adversely affects the device.
Aspect 3 defines a backlighting element with an EL panel for illuminating the back of visually presenting means of a device, the backlighting element being characterized in that one of the upper and lower electrodes, which form a light emitting section of the backlighting element, is formed so that the light emitting section is disposed occupying a part of an area defined by a configuration of light emitting means in the EL panel.
As defined in aspect 4, the light emitting section takes the form of any of a lattice, a stripe and a slant lattice.
As defined in aspect 5, the visually presenting means illuminated is a liquid crystal panel constituting a display unit of a device, and the light emitting section is divided into a plurality of segments corresponding to display lines of the liquid crystal display panel or display units consisting of display characters.
As defined in aspect 6, the visually presenting means illuminated is a liquid crystal panel constituting a display unit of a device, and the light emitting section includes a plurality of light emitting segments corresponding to display lines of the liquid crystal display panel or display units consisting of display characters, the plurality of light emitting segments being selectively driven.
In the backlighting element defined in aspects 3 to 6, one of the upper and lower electrodes, which form a light emitting section of the backlighting element, is formed so that the light emitting section is disposed occupying a part of an area defined by a configuration of light emitting means in the EL panel. Therefore, the actually light emitting area of the light emitting potion may be reduced. The power consumed when the backlighting element is driven is lessened for a given level of luminance brightness. This leads to reduction of the power consumption during the backlighting.
Aspect 7 defines a backlight device comprising: a backlighting element with an EL panel for illuminating the back of visually presenting means of a device, the backlighting element being constructed in that one of the upper and lower electrodes, which form a light emitting section of the backlighting element, is formed so that the light emitting section is disposed occupying a part of an area defined by a configuration of light emitting means in the EL panel, and light diffusing means for diffusing light emitted from the light emitting section. As defined in aspect 8, the light diffusing means is formed by interposing a sheet or plate like member having a light diffusing function between the backlighting element and an illuminated member, by coating the surface of the backlighting element with light diffusing material, or by coupling an optical member having light diffusing function to the backlighting element or an illuminated member.
In the construction defined in aspects 7 and 8, one of the upper and lower electrodes, which form a light emitting section of the backlighting element, is formed so that the light emitting section is disposed occupying a part of an area defined by a configuration of light emitting means in the EL panel. Therefore, the actually light emitting area of the light emitting potion may be reduced. The power consumption during the backlighting is reduced. A dark and bright pattern of the light emitting section of the backlighting element is diffused, so that uniform illumination is obtained. No unnatural visual feeling is presented to the user.
Aspect 9 further defines the backlight device of any of aspects 1, 2 and 7 such that the backlighting device further comprises a light storage member capable of storing backlight from the light emitting means of the backlighting element or natural light and spontaneously emitting light. As defined in aspect 10, the light storage means is formed by interposing a sheet or plate like member containing light storage material between the backlighting element and an illuminated member, by coating the surface of the backlighting element with light storage material, or by use of the backlighting element containing light storage material.
In the backlight devices of aspects 9 and 10, an illumination effect is secured if the backlighting element is not lit because of use of the light storage member. The on time of the backlighting element is reduced, and the device power consumption is reduced. Further, even when the backlighting element is intermittently lit, the user is insensitive to its flicker.
Aspect 11 further defines the backlighting device of aspect 7 such that the visually presenting means illuminated is a liquid crystal panel constituting a display unit of a device, and the light emitting section is divided into a plurality of segments corresponding to display lines of the liquid crystal display panel or display units consisting of display characters, and the backlighting device further comprising drive control means for selectively driving the plurality of segments of the light emitting section to locally light on and off the light emitting section.
In the backlight device of aspect 11, the light emitting section of the backlighting element is divided into a plurality of light emitting segments. Those segments are selectively lit on and off. Therefore, the backlighting element may be driven only when its drive is required. The power consumption during the backlighting is reduced.